1. Field of the Invention
The present invention relates to a hook screw driver that reliably clamps a hook screw during operation.
2. Description of the Related Art
Taiwan Patent Publication No. 364439 discloses a hook screw driver comprising a body and two discs. Each of two ends of the body has a compartment for partially receiving a respective disc. The respective disc has a retaining section on each of two ends thereof, the retaining section having a plurality of spaced blocks that constitute a plurality of grooves for securely retaining a hook portion of a hook screw of a size that may be varied in a range. In use, the respective disc is removed from the respective compartment, the hook portion of the hook screw is placed in the proper retaining section, and the disc is then placed in the respective compartment. The hook portion of the hook screw is retained in place by the blocks. However, it was found that the retaining sections that suit to the hook screws manufactured by one manufacturer may not suit the hook screws manufactured by other. Further, it was found that the hook screw tended to sway such that the user had to remove it from the respective disc and put it back for several times during operation.
U.S. Pat. No. 6,026,715 discloses a hook screw driver having a holding section and an end section. The holding portion has a first part integral with the end section and a second part. Each part has an inner side that includes a compartment defined in a first end thereof. A soft holding member is received in the compartment and made of a highly deformable, highly frictional material for securely holding a hook portion of a hook screw. A second end of each part has a threading defined in an outer side thereof. A retainer ring with an inner threading is moved forward along a longitudinal direction to threadedly engage with the threading on each part after the hook portion of a hook screw is placed on one of the soft holding members. Thus, the hook portion of the hook screw is held by the hook screw driver. However, it was found that the retainer ring could not move forward to tightly clamp the hook portion of a hook screw having a relatively large thickness. Further, the threading on each part of the hook screw driver is exposed and is thus apt to wear as a result of impingement by other tools in a box in which the hook screw driver is received. Thus, the hook screw driver lost the clamping function. Further, the second part can be opened for receiving/removing the hook screw only when the retainer ring is completely disengaged from the threading on each part, which is inconvenient to the user.